T-Squares including protractors are known and are used for measuring angles.
For instance, U.S. Pat. No. 936,157 (Phenix) describes a measuring instrument to be used as a bevel or a square having a member 1 having formed therein a protractor extending between two points of the member intermediate the length thereof, and a second member 4 pivotally attached to member 1 by a bolt 3, the connection between the two members being centrally of the protractor 2. In use, the member 4 is moved on its pivot 3, the angle of the level being assured by the protractor 2. A binding screw 9 contacts the protractor 2 in engagement with an arm 8 for binding the member 4 thereto and as the protractor is carried by the member 1, the member 4 will be held against movement (see FIG. 1). U.S. Pat. No. 1,083,376 (Robinson) describes a combination measuring instrument having two arms pivotally hinged to one another by a pivot. A protractor arc or scale engages both arms so that its center is coincident with the axis of the pivot 3, 7, and 8. A slot in the protractor arc is used to guide the two arms for ready adjustment of the angle therebetween in conjunction with two screws for clamping the arm to the protractor arc (see FIG. 1). U.S. Pat. No. 2,247,327 (Brady) describes a measuring instrument similar to that of Robinson. In the device of Brady one of the hinged arms was substituted with a level which has formed therein end slots 6 and an intermediate slot 7 having therein spirit bubble tubes for ascertaining when work is level (see FIG. 1).
U.S. Pat. No. 4,611,407 (van Gorp) describes a pivot assembly for a guide or marking tool (10) comprising a stock (12) with a reference edge (31) alignable with a desired datum (36), a blade (13) with a sighting, guiding or marking edge (16) and a semi-circular segment (18) provided with angle indicia (19). The stock (12) is pivotally connected to the blade (13) so that the angle between the reference edge (31) and the sighting edge (16) may be adjusted to a predetermined setting and the pivot axis (9) of the stock (12) relative to the blade (13) is located at the intersection between the reference edge (31) and the sighting edge (16) at all relative angular settings between the stock (12) and the blade (13). Pivoting of the stock and blade is effectuated by arcuate guide tracks on the stock (12) mating with corresponding depending flanges on the undersurface of segment (18). A slot (22) concentric with the guide tracks is provided in the segment (18), whereby lightening of the thumb wheel (24) clamps the segment (18) firmly against the upper surface (28) of the stock (12).
U.S. Pat. No. 4,736,524 (King) describes a framing T-Square and protractor wherein the head of the T-Square and the elongated rule thereof are connected by means of a ballbearing allowing the rule portion to be free-swinging with respect to the head, which is in the form of a rectangular plate having a protractor scale thereon marked in degrees and auxiliary scales marked with inches of rise per 12 inches of run for common rafters and for hip and valley rafters. A rectangular panel is hingedly attached to the plate on a hinged line normally at right angles to the elongated rule; a friction locking mechanism permits the rule to be locked at any desired angle relative to the plate and panel. The rule, plate, and panel are marked on the back with rafter tables and other data including run lengths and protractor angle settings useful in roof framing and other construction or carpentry work. A vernier scale on the front of the panel facilitates setting of angle measurements to an accuracy of one-tenth of a degree.
U.S. Pat. No. 6,954,990 (Ellis) describes a measuring device for carpenters, roofers and other tradesmen. The device is made of relatively lightweight plastic and has a variety of uses. The elongated base is rectangular in cross sectional and includes a scale for measuring distances along one side. Pivotally affixed to the base is a level which can be locked against a protractor (also affixed to the base) at any angle between zero and ninety degrees (0.degree.-90.degree.). Roof pitches, gradients and other angles can be determined or set in a simple, easy to learn manner. FIG. 1 illustrates a measuring device 10 seen in perspective fashion having base 11, level 12 and protractor 13. As shown in FIGS. 1, 2, and 7, slots 24, 24′ are defined in base 11 and level 12 to accommodate protractor 13. Protractor 13 is rigidly mounted within base 11 such as by frictionally fitting therein or with conventional glues or adhesives. Level 12 is also mounted to base 11 by hinge 15. Window 16 within level 12 is preferably formed from a transparent rigid plastic material such as a clear polycarbonate or polyacrylate and is affixed to level 12 as seen in FIGS. 1, 3, and 4. Window 16 includes aperture 17 through which threaded locking member 18 is positioned. Locking member 18 passes through window aperture 17 of window 16 and slot 19 of protractor 13 whereby, effectively bolt nut 14, as seen in FIG. 2, is used to tighten threaded member 18 in place. Locking member 18 can be manually tightened to lock level 12 in any number of positions along scale 30 having line gradients 31, relative to base 11.
U.S. Pat. No. 7,188,427 (Johnson) describes a multi-task protractor apparatus having the capabilities of a rotating protractor, adjustable triangle, ruler, miniature leveler, framing square and roof angle finder is disclosed. The multi-task protractor accurately measures angles and slopes and provides two straight edges for constructing angles and triangles. The multi-task protractor has a) a ruler of a selected length, having a first edge and a second edge, a first side and a second side, a length and a width, a first connector opening, at least one second connector opening and at least one leveling vial; b) a rotatable arm having a first and a second end, a first and a second side, a first arm connector opening near the first end of the rotatable arm and a second arm connector opening and being connected to the ruler by a first connector connecting the first connector opening and the first arm connector opening for rotation about the first connector or positioning in selected fixed orientations relative to the ruler and the first connector wherein the rotatable arm includes at least one opening positioned and configured to be positioned over at least one vial when the rotatable arm is positioned over the first side of the ruler; and; c) a protractor comprising a 180 degree arc having an arc inside and an arc outside, a first and a second end, a passageway extending around the 180 degree arc between the arc inside and the arc outside and at least one set of graduations on at least one side of the protractor, the protractor being connected to the ruler and to the rotatable arm by at least one of a second connector connecting at least one of the plurality of second connector openings, and the passageway and a third connector in the second arm connector opening to enable sliding and rotationable movement of the protractor relative to the rotatable arm and to enable positioning the protractor in selected fixed positions relative to the ruler and the rotatable arm.
U.S. Pat. No. 7,278,217 (Mills) describes a trigonometric teaching aid for providing students with real life applications for the principles of trigonometry includes a transit assembly having a sight tube with cross hairs, a level and an upper protractor pivotally connected to an upper end of a vertical scale, and a base assembly including a lower protractor pivotally connected to a lower end of the scale member. By levelling the transit assembly and measuring the angles of inclinations at the protractors, student using trigonometric formulas, tables and classroom lessons can determine physical measurements of real life objects.
The conventional devices involve a T-square style part and a protractor part. However, the conventional devices appear impractical and inefficient for measuring angles and scales in roof framing due to their small size and unbalanced construction from side to side.
Accordingly, there would be a need for a simpler more robust T-square including a protractor adapted for use in construction for measuring large roofing and/or wallboard materials. Such a device would have a solid construction adapted for inscribing lines at various angles on large stock material, for example 4 ft×8 ft, commonly used in the construction industry.
The invention, was, thus, made in recognition of the need for a simpler, robust, and maintenance free T-square and protractor adapted for measuring large material used in roof framing and otherwise in the construction industry.